Project Summary (Abstract) Osteoporosis, a silent debilitating bone disease, results when the rate of bone resorption (by osteoclasts) is much greater than the rate of bone formation (by osteoblasts) causing bone loss, deterioration of bone quality, leading to decreased bone strength and bone fragility and susceptibility to bone fracture. Current FDA-approved drugs are shown to prevent further bone loss but have not been shown to restore bone already lost to the disease. Furthermore, many of these drugs have serious side effects (e.g., breast cancer from estrogen therapy, osteonecrosis of the jaw and delayed healing from bisphosphonate-based drugs). The over-all objective of the study is to develop novel innovative compounds, MZF-CaP and MZ- CaP/FF (a combination of MZ-CaP and flavan/flavonoids, FF), that will be safe, affordable and effective for prevention and reversal of bone loss. Preliminary data showed that MZF-CaP formulations administered as a supplement or by injection prevented bone loss induced by mineral deficiency or estrogen deficiency (ovariectomy) in rats. For the continuing study, the specific aims are to: (1) prepare (a) MZF-CaP (with low fluoride) and (b) MZ- CaP/FF (without fluoride combined with flavan/flavonoids, FF, known to inhibit cytokines associated with bone resorption) and characterize their properties (composition, ion release, dissolution) and the in vitro response elicited from bone-forming (osteoblasts) or bone-resorbing (osteoclasts) cells; (2) evaluate the effect of selected MZF-CaP and MZ-CaP/FF preparations as supplement on the (a) prevention and (b) restoration or reversal of bone loss induced by ovariectomy or mineral deficiency, compared with calcium + vitamin D supplement; (3) evaluate the effect of MZF-CaP and MZ-CaP/FF on prevention of bone loss in a larger animal model (sheep); and (4) determine the effects of MZF-CaPs and MZ-CaP/FF on the following levels: (a) molecular (gene expression) and cellular (osteocyte density); (b) biomechanical (bone strength, bone density); (c) microstructural (cortical and trabecular bone thickness, trabecular bone porosities, anisotropy); (d) biochemical (matrix/mineral ratio, degree of bone mineralization)' and biomineral (bone mineral composition, crystallinity and dissolution properties). Analytical methods will include: x-ray diffraction, FT-IR spectroscopy, thermogravimetry, scanning electron microscopy, micro- computed tomography. Significance: Results from the proposed studies could lead to the development of safe and affordable therapy that will target both prevention and reversal of bone loss due to osteoporosis and other bone- deficient diseases. These results will greatly impact public health and alleviate the tremendous socio- economic burden associated with osteoporosis.